Flight of the Antares – Orbital closing in on long-awaited debut

January 22, 2013 by Chris Bergin

The Antares launch vehicle will soon make its debut flight, ahead of an important year for Orbital’s Commercial Resupply Services (CRS) contract requirements. The test flight of the new launch vehicle will pave the way for a demo mission to the International Space Station (ISS) in May, involving the first use of the Cygnus spacecraft.

Antares:

The Antares – formerly known as Taurus II – is the first cryogenically powered launch vehicle produced by Orbital Sciences, as well as its largest rocket to date.

The main engine for the first stage of the Antares is the Aerojet produced AJ-26.

These engines are a rebuilt version of Soviet NK-33, originally intended for the massive N-1 launch vehicle that was in direct competition with NASA’s Saturn V.

Aerojet later bought the engines – which had never been used – and added modern electronics and other performance enhancements.

The full-duration test was the eleventh AJ26 engine tested at the NASA facility, which provided acceptable results that will allow for the hardware to be shipped to the Wallops launch site in Virgina for integration with the Antares rocket.

Antares was scheduled to spread its wings in 2012. However, delays to Antares’ schedule were caused by problems related to the completion of construction work on the launch pad’s propellant handling and pressurization systems. However, the vehicle’s path to launch now appears to be much clearer.

This allowed for the new vehicle to receive its lifeblood for the first time, as engineers conducted wet dress rehearsals – known as cold flow testing – the last of which is expected to take place in the coming days.

This will allow for February’s key milestone of the hot fire test, with the Antares firing its AJ26s whilst held down at the launch pad. Engineers will review the results of the test over the weeks that follow, with a goal of approving Antares to make its first launch into space.

Expected in March or early April, this test flight mission will task Antares with lofting a Cygnus mass simulator payload that will be heavily instrumented to gather data on the launch environment aboard Antares.

In addition, four small “pico satellites” will be deployed from two dispensers that will be integrated with the mass simulator.

Providing no major issues were found with the test launch, Orbital will then move on to their final requirement under the Commercial Orbital Transportation Services (COTS) contract – a full demo mission.

The Cygnus spacecraft consists of an advanced Service Module and a Pressurized Cargo Module (PCM). The Service Module incorporates avionics, power and propulsion systems from Orbital’s flight-proven LEOStar and GEOStar satellite product lines.

Thales Alenia Space are providing Orbital with the pressurized modules for cargo missions to the ISS. The first PCM was followed by three more units in “standard” configuration, capable of transporting up to 2,000 kg of cargo each, along with five “enhanced” configuration units to follow, boosting payload capacity to 2,700 kg.

Per L2 mission overview documentation, Antares will launch Cygnus into orbit for five to six days of demos during the period of far field phasing. Future missions will only require a standard three days prior to arriving at the ISS.

There will be two key operational phases for the opening part of the mission, the Integrated Launch Operations Phase (ILOPS), for ascent and insertion, handing over to the Phasing Operations Phase (POPS), for the pursuit of the ISS.

For Cygnus to safely arrive in the ISS’ back yard, extra caution is required when entering the ISS’ “Keep Out Sphere (KOS)”.

Due to stray light and reflections coming off the ISS, the SpaceX team had to recalibrate – successfully – one of the beams to narrow its field of view. The problem did not reoccur during Dragon’s CRS-1 mission.

Given real-time tracking of undock and flyaround had already been previously performed during STS-131, the Neptec TriDAR team took the unique opportunity to produce 3D and thermal movies of the last Shuttle based ISS flyaround operation.

The ISS and Cygnus – as with all visiting vehicles, including Dragon - also need to show they have a strong communication link, required not least for the ability to manually abort the approach – or at least retreat – in the event of problems. This phase of the mission is called the Joint Operations Phase (JOPS).

This critical approach period is called Proximity Ops, with Cygnus using the JEM PROX system for direct communications with ISS, effectively resulting in the use of the same system Japan’s HTV uses for arriving at the ISS, as much as there will be a number of different settings employed for Cygnus’ arrival.

As with Dragon, Cygnus will stalk the ISS, slowly creeping up to its target via a large series of demos to test its systems. As the Orbital spacecraft sneaks up the R-bar, under the ISS, it will enter the KOS.

Once inside the KOS, Cygnus will demonstrate that it can hold and retreat, prior to receiving the go – via polling – to proceed.

With its TriDAR locked on – the tenth demo of the approach at this point – a final go will be given for Cygnus to approach to the capture point.

Once berthed, the ISS crew will begin vestibule ops and Cygnus activation via ISS power jumpers on rendezvous day, documented as a nine hour procedure. Hatch opening and ingress will occur on the following mission day.

Cygnus’ hatch is very similar to a standard US segment hatch, albeit slightly smaller, making it a similar sight to the ISS crewmembers. A ventilation duct will be hooked up, and the spacecraft cleared of any dust prior to becoming safe to ingress without eye protection and masks.

Cygnus currently supports a berthed duration of up to 30 days, with this period of the mission classed as the Berthed Operations Phase (BOPS).

It is not yet known what cargo Cygnus will be manifested with for this demo mission, although a basic sequence for cargo ops has already been written.

This involves the crew removing the “top layers” on PORT and STBD pallets to make room in PCM. They will then remove components of the Secondary Structure as required, ahead of emptying the FWD and AFT pallets to gain access to the Standoff pallets, which they will empty and repack.

The reverse sequence will be employed until the vehicle has been repacked, although all the return cargo won’t be classed as downmass, because – unlike Dragon – Cygnus won’t be returning to the ground or water. Instead, it’ll be sent on a path to a destructive re-entry.

The final phase of the mission – a reverse of the berthing procedures – is called the Descent & Reentry Operations Phase (DROPS), as Cygnus ends its life in a disposal corridor during entry, hopefully with a smile on its face, following a successful demonstration that paved the way for its siblings to each take a turn in providing full CRS operations.

The deal to carry out ISS resupply flights – under the $1.9 billion CRS contract – encompasses eight missions through to 2015 carrying approximately 20,000 kg of cargo to the ISS.